Over the last decade, the average number of callouts the SAR receives every year is 1,950. Prince William's unit, the RAF Valley, responds to a huge number due to the area being popular with walkers and climbers.

In a team of four, Prince William starts his day with a morning briefing from the crew finishing their shift.

As soon as they clock on, the crew are at 'Readiness State 15' from 8am to 10pm. This means they must be airborne within quarter of an hour of receiving a distress call. They move to 'Readiness State 45' from 10pm until their 24-hour shift ends, meaning they have more time to plan and prepare the night-time operations.

Often, the crew fly into perilous conditions including gales, rain and poor visibility. They operate a Sea King Mark 3, which has two pilots, a winchman and a radar/winch operator. The helicopter can carry 17 passengers and can fly 250 miles over six hours.

Before going out, Prince William must check his own kit, including the airframe, navigation systems and the hydraulics. They must then go and complete the mission, be it rescuing walkers from the mountains of north Wales, or passengers on a sinking vessel in the Irish Sea.

During the down time, when the crew is not out saving lives, the Duke of Cambridge might be found in the crew-room eating or playing on computer games like Call of Duty.

However, as callouts are unpredictable, they also spend much of their time planning and taking part in SAR training exercises.

At the end of the shift, Prince William then de-briefs the new crew and heads home to his wife, the Duchess of Cambridge.